EVAP System High Purge Flow
Indicates high flow in the EVAP purge system.
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What it means (plain English)
The car’s computer detects that there’s too much air or vapor being pulled from the fuel tank into the engine, which can mess with fuel efficiency and emissions.
What the computer is actually seeing
The engine control module (ECM) monitors the amount of vapor coming from the EVAP system. When it sees more than preset limits (typically over 0.80 volts from the purge flow sensor), it sets this code.
What a healthy reading looks like
The expected signal from the purge valve should be between 0 to 100% duty cycle. A reading over 80% while idling may trigger the code.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connector for the purge valve. Ensure there are no shorts or breaks. If damaged, repair or replace the wiring.
- 22. Check the fuel cap for damage or improper sealing. Ensure it's tight and in good condition. Replace if necessary.
- 33. Test the purge valve operation by applying 12V directly to the valve. It should open and close with no sticking. If it doesn’t, replace it.
- 44. Inspect the intake manifold for vacuum leaks, using propane or carb cleaner to check for RPM changes. Fix any leaks found.
- 55. Clear the code and perform a drive cycle. If it returns, further diagnose the EVAP system or consult a service manual for specifics.
Common causes
- Faulty purge valve
- Clogged fuel tank vent
- Vacuum leaks in the EVAP system
- Faulty fuel cap or seal
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's mostly safe but will affect fuel efficiency and emissions. Get it checked soon.
Will this code come back after clearing it?
If the underlying problem isn't fixed, yes, it will likely return.
Why does this code pair with P0446?
Both codes indicate issues in the EVAP system, usually related to vapor flow and pressure.
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